1. Field of the Invention
The present invention relates to a flat type vibrating motor, and more particularly, to a flat type vibrating motor suitably applied to an apparatus operated by a battery.
2. Description of the Related Art
As mobile communication apparatuses becomes slim and are miniaturized recently, a flat type vibrating motor generally used becomes slim gradually.
Under this trends, crucial objects of the flat type vibrating motor is to reduce a volume of the flat type vibrating motor itself in order to reduce a volume of the mobile communication apparatus, and to reduce power consumption in order to lengthen life of the battery mounted within the mobile communication apparatus.
To achieve the above-mentioned objects, Japanese Patent Publication No. 2004-147468 (a patent document 1) is known as an alternative capable of reducing a volume of a flat type vibrating motor itself and obtaining sufficient strength.
FIG. 1 is a vertical cross-sectional view of the flat type vibrating motor disclosed in the above Japanese Patent, and FIG. 2 is a horizontal cross-sectional view of FIG. 1.
Referring to FIGS. 1 and 2, the vibrating motor 10 includes a lower cover 11 and an upper cover 13 coupled to each other to constitute a predetermined space in an inside of the vibrating motor 10. A lower portion and an upper portion of a shaft 15 are supported by the lower cover 11 and the upper cover 13.
A stator base 17 is disposed on the lower cover 11, and a coil 19 adheres on the stator base 17. Also, a bearing 21 is provided on an outer periphery of the shaft 15. An eccentric rotor yoke 23 is fixed on an outer periphery of the bearing 21. Also, a magnet 25 and a weight 27 are provided on a lower surface of the rotor yoke 23.
With this construction, when a current is supplied to the coil 19, the magnet 25, the weight 27, and the rotor yoke 23 are rotated by interaction between the coil 19 and the magnet 25, and vibration is generated by eccentricity caused by the weight 27.
In this flat type vibrating motor, a control integrated circuit (IC) 30 and a Hall device 20 are disposed inside a case on the stator base 17, and a six pole-magnet 25 and two coils 19 are series-connected.
Meanwhile, since a thickness of the coil 19 has a thin thickness of 0.5-0.6 mm, and particularly, the magnet 25 has a thin thickness of 0.4-0.5 mm to achieve a slim profile of the vibrating motor 10, a Nd—Fe—B bonding magnet is applied instead of a Nd—Fe—B sinter magnet. However, since the Nd—Fe—B bonding magnet has a lower magnetic flux density than that of the Nd—Fe—B sinter magnet, a two-coil driving type vibrating motor has problems of weak torque and a limitation in reducing a consumed current.
In detail, torque of the vibrating motor is proportional to product of the number of the coil's wiring and a consumed current. When torque is reduced with a constant number of the coil's wiring, a consumed current can be reduced. However, when torque is reduced, an amount of vibration is reduced, which is not preferable.
A related art vibrating motor has a problem of constantly consuming a driving current of about 80-85 mA in order to obtain torque of a predetermined level or more. This excessive driving current of the vibrating motor accelerates battery consumption of a mobile communication apparatus, reducing an operating time of a mobile communication apparatus.
Of course, a method of increasing the number of wirings wound on the coil can be proposed. However, when the number of the wirings wound on the coil is increased, a volume of the vibrating motor itself is increased, which is not preferable.